L\u2019un est color\u00e9 et vit dans les rivi\u00e8res d\u2019Am\u00e9rique latine, l\u2019autre est aveugle, d\u00e9pigment\u00e9 et habite dans l\u2019obscurit\u00e9 des grottes mexicaines, pourtant ce sont les m\u00eames poissons\u00a0:\u00a0Astyanax mexicanus. Des chercheurs de l\u2019Institut des neurosciences Paris-Saclay (CNRS\/Universit\u00e9 Paris-Sud) ont recherch\u00e9 les m\u00e9canismes embryonnaires \u00e0 l\u2019origine de leurs diff\u00e9rences morphologiques et comportementales.<\/p>\n
Comment les sp\u00e9cimens cavernicoles ont-ils \u00e9volu\u00e9 afin de survivre dans un tel environnement ?<\/p>\n
L’\u00e9volution du d\u00e9veloppement c\u00e9r\u00e9bral et ses cons\u00e9quences comportementales est un sujet majeur pour comprendre comment les vert\u00e9br\u00e9s colonisent les environnements nouveaux. Astyanax mexicanus est un mod\u00e8le de choix pour aborder cette question.<\/p>\n
Ce poisson pr\u00e9sente deux morphotypes: une forme d’habitat de surface qui habite les rivi\u00e8res de l’Am\u00e9rique Centrale et du Sud, et une forme cavernicole compos\u00e9e de plusieurs populations vivant dans l’obscurit\u00e9 totale et permanente des grottes mexicaines.<\/p>\n
Les poissons cavernicoles ont \u00e9volu\u00e9 vers des traits r\u00e9gressifs – les plus spectaculaires \u00e9tant la perte des yeux et de la pigmentation – mais ils ont aussi d\u00e9velopp\u00e9 plusieurs traits constructifs tels qu’une m\u00e2choire plus large, plus de papilles gustatives, ou des \u00e9pith\u00e9liums olfactifs plus importants, et aussi de nombreux changement comportementaux. Parmi les plus frappants\u00a0: les morphes cavernicoles dorment tr\u00e8s peu et nagent en permanence.<\/p>\n
Les chercheurs de l\u2019Institut des Neurosciences Paris-Saclay (CNRS\/Universit\u00e9 Paris-Sud) ont observ\u00e9 qu\u2019un nombre diff\u00e9rent de certains neurones se d\u00e9veloppait dans l\u2019hypothalamus chez les embryons des deux sp\u00e9cimens. Cette variation naturelle dans le d\u00e9veloppement c\u00e9r\u00e9bral impacte non seulement la morphologie des poissons cavernicoles mais aussi leur comportement.<\/p>\n
En intervenant sur le d\u00e9veloppement neuronal des larves du poisson cavernicole, les chercheurs sont parvenus \u00e0 leur faire mimer le comportement du poisson de surface. Ce travail r\u00e9v\u00e8le donc de nouvelles variations sous-jacentes \u00e0 l’\u00e9volution et \u00e0 l’adaptation des poissons cavernicoles \u00e0 leur environnement extr\u00eame. Ces variations en nombres de neurones trouvent leur origine dans des processus embryonnaires tr\u00e8s pr\u00e9coces, qui se produisent pendant les dix premi\u00e8res heures apr\u00e8s la f\u00e9condation, lorsque l\u2019embryon n\u2019est encore qu\u2019une \u00ab\u00a0boule de cellules\u00a0\u00bb.<\/p>\n
<\/p>\n
R\u00e9f\u00e9rences :<\/p>\n
Developmental evolution of the forebrain in cavefish, from natural variations in neuropeptides to behavior,\u00a0Alexandre Ali\u00e9, Lucie Devos, Jorge Torres-Paz, Lise Prunier, Fanny Boulet, Maryline Blin, Yannick Elipot et\u00a0Sylvie R\u00e9taux, eLife, 6 f\u00e9vrier 2018.\u00a0doi.org\/10.7554\/eLife.32808<\/p>\n
Contact chercheur:<\/p>\n
Sylvie R\u00e9taux<\/p>\n
Institut des Neurosciences Paris-Saclay<\/p>\n
D\u00e9veloppement & \u00c9volution du cerveau ant\u00e9rieur<\/p>\n
retaux@inaf.cnrs-gif.fr<\/p>\n
<\/p>\n
The same fish but a few more Hypocretin neurons<\/strong><\/p>\n New insight into the development and function of Mexican cavefish brains reveals how the animals adapted their behaviour to cope with extreme environments.<\/p>\n There are two forms of A. mexicanus: surface-dwelling fish that inhabit rivers in south and Central America, and fish that live in the total and permanent darkness of Mexican caves. The cavefish display striking differences from their river-dwelling counterparts, including the loss of sleep that makes them a potential model to study human sleep disorders such as insomnia.<\/p>\n In a study published in eLife, researchers from the French National Center for Scientific Research (CNRS) and Universit\u00e9 Paris-Saclay demonstrate how the developmental evolution of the brain in cave-dwelling Astyanax mexicanus (A. mexicanus) underlies the evolution of its survival behaviors. A second study from the US, published at the same time in eLife, suggests higher levels of hypocretin (HCRT) in the cavefish brain \u2013 a chemical compound associated with human narcolepsy \u2013 accounts for the loss of sleep in these animals.<\/p>\n \u201cA. mexicanus cave-dwellers have developed this and other beneficial behaviors that allow them to live in adverse environments,\u201d says senior author Sylvie R\u00e9taux, Group Leader at CNRS, Paris-Saclay Institute of Neuroscience. \u201cThis makes them a prime model to study the evolution of brain development and its behavioral consequences, providing greater understanding of how vertebrates colonize more unusual locations.\u201d<\/p>\n In their study, R\u00e9taux and her team compared the development and natural variations of anatomy in the brains of both surface and cave-dwelling A. mexicanus embryos and larvae, highlighting specific differences in the numbers of neurons between the two forms. \u201cWe discovered a higher number of HCRT cells developing in the brains of cave-dwelling fish compared to surface-dwellers,\u201d explains postdoctoral researcher Alexandre Ali\u00e9. \u201cBy manipulating the numbers of HCRT neurons, we were able to link these to increased activity levels in the animals.\u201d Jorge Torres-Paz, also a postdoctoral researcher at CNRS, adds: \u201cInterestingly, we found that the variation in HCRT neuron numbers stems from very early embryonic events, which occur as early as within the first 10 hours after fertilization, when the embryo is still like a ball of cells. This suggests the mechanisms that lead to the loss of eyes could be shared in part with those that control developmental evolution of brain and behaviour, including sleep.\u201d<\/p>\n These findings show that developmental evolution of the cavefish brain drives evolution in the animals\u2019 behavior. More generally, they also support a role for HCRT in relation to sleep in other animals, providing a new system for investigating sleep differences throughout the entire animal kingdom.<\/p>\n","protected":false},"excerpt":{"rendered":" L\u2019un est color\u00e9 et vit dans les rivi\u00e8res d\u2019Am\u00e9rique latine, l\u2019autre est aveugle, d\u00e9pigment\u00e9 et habite dans l\u2019obscurit\u00e9 des grottes mexicaines, pourtant ce sont les m\u00eames poissons\u00a0:\u00a0Astyanax mexicanus. Des chercheurs de l\u2019Institut des neurosciences Paris-Saclay (CNRS\/Universit\u00e9 Paris-Sud) ont recherch\u00e9 les m\u00e9canismes embryonnaires \u00e0 l\u2019origine de leurs diff\u00e9rences morphologiques et comportementales. Comment les sp\u00e9cimens cavernicoles ont-ils […]<\/p>\n","protected":false},"author":4,"featured_media":8931,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[25],"tags":[31],"class_list":["post-8934","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-actualite-en"],"publishpress_future_action":{"enabled":false,"date":"2026-04-24 14:47:38","action":"change-status","newStatus":"draft","terms":[],"taxonomy":"category"},"publishpress_future_workflow_manual_trigger":{"enabledWorkflows":[]},"_links":{"self":[{"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/posts\/8934","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/comments?post=8934"}],"version-history":[{"count":1,"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/posts\/8934\/revisions"}],"predecessor-version":[{"id":8935,"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/posts\/8934\/revisions\/8935"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/media\/8931"}],"wp:attachment":[{"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/media?parent=8934"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/categories?post=8934"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.neurosciences.asso.fr\/en\/wp-json\/wp\/v2\/tags?post=8934"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}